This application is related to and incorporates by reference Japanese patent application number 2001-308906, which was filed on Oct. 4, 2001.
The present invention relates to an ejector circuit having an ejector that increases the suction pressure of a compressor by converting expansion energy into pressure energy while expanding the refrigerant under a reduced pressure in a vapor compression refrigerating circuit, which transfers heat from the low-temperature side to the high-temperature side.
The term xe2x80x9cejector circuitxe2x80x9d denotes a cooling circuit in which refrigerant is expanded in an ejector under a reduced pressure and a gas-phase refrigerant evaporated in an evaporator is drawn, while converting expansion energy into pressure energy to increase the suction pressure of a compressor.
In the cooling circuit, which reduces the pressure of the refrigerant by pressure reduction means in an isentropic manner (hereinafter, such a circuit is referred to as an expansion valve circuit), such as by an expansion valve, the refrigerant flowing out of the expansion valve flows into the evaporator. In the ejector circuit, on the other hand, refrigerant flowing out of the ejector flows into a gas-liquid separator, while liquid-phase refrigerant separated in the gas-liquid separator is supplied to the evaporator and gas-phase refrigerant separated in the gas-liquid separator is drawn into the compressor.
In other words, the expansion valve circuit represents a single flow of refrigerant where the refrigerant is circulated through a compressor, a radiator, an expansion valve, an evaporator, and the compressor in this order. In the ejector circuit, shown in FIG. 8, there are different flows of refrigerant. One flow allows the refrigerant to circulate through a compressor 100, a radiator 200, an ejector 400, a gas-liquid separator 500, and the compressor 100 in this order (hereinafter, such a flow is referred to as a driving flow) while the other allows the refrigerant to circulate through the gas-liquid separator 500, an evaporator 300, the ejector 400, and the gas-liquid separator 500 in this order (hereinafter, such a flow is referred to as a suction flow).
Therefore, the removal of frost that has formed on the evaporator (i.e., defrosting) can be performed by allowing a flow of a high-temperature refrigerant into the evaporator by fully opening the expansion valve. In the ejector circuit, on the other hand, the high-temperature refrigerant flowing through the radiator (the driving flow) and the suction flow through the evaporator are different. As a result the driving flow cannot be supplied to the evaporator, and defrosting cannot be performed.
Thus, as shown in FIG. 9, the present inventors investigated an ejector circuit by providing: a hot-gas passage (a bypass pipe arrangement) 600 provided for transferring a high-temperature refrigerant (hot gas), discharged from a compressor 100, to the inlet side of the evaporator 300 for the refrigerant while bypassing a radiator 200 and an ejector 400. A defrost control valve 610 is provided for opening and closing the hot-gas passage 600, so that a defrosting operation is performed by opening the defrost control valve 610. However, this can result in the problems described below.
In the trial apparatus of FIG. 9, during normal operation, in which the refrigerant is evaporated in the evaporator 300, the defrost control valve 610 is closed to prevent refrigerant discharged from the compressor 100 from passing through the hot-gas passage 600. However, the refrigerant flowing from the lower pressure side (on the side of the evaporator 300) into the hot-gas passage 600 is retained in the hot-gas passage 600. Therefore, there is the possibility that the amount of refrigerant available for normal operation will be reduced.
Thus, there is a need to use a larger amount of refrigerant in the circuit to compensate for the amount of refrigerant retained in the hot-gas passage 600. This results in an increase in the production cost of the ejector circuit. This also results in an unusual increase in the pressure at the high-pressure side if there is an overload condition.
In the expansion valve circuit, there is one variation that performs a defrosting operation by providing a hot gas passage to introduce hot gas to the evaporator without passing through the radiator and the expansion valve. In the expansion valve circuit, the hot-gas passage is connected in series with a compressor, so that refrigerant retained in the hot-gas passage can be drawn out by the compressor during normal operation.
On the other hand, in the ejector circuit, the pressure difference generated in the ejector circulates the refrigerant under a low pressure. Therefore, it is difficult to generate a sufficient drawing force to draw the refrigerant retained in the hot-gas passage. As a result, there is a high possibility that refrigerant flowing into the hot-gas passage will be retained in the hot-gas passage.
In view of the above problems, an object of the present invention is to decrease the amount of refrigerant required by the refrigeration circuit.
To attain this object, the invention includes a compressor for drawing and compressing refrigerant; a radiator for cooling the refrigerant discharged from the compressor; an evaporator for evaporating the refrigerant; an ejector having a nozzle for expanding the refrigerant under reduced pressure by converting a pressure energy of the high-pressurized refrigerant flowing out of the radiator into velocity energy, and a suction device for drawing a gas-phase refrigerant evaporated in the evaporator by a flow of refrigerant at a high speed being ejected from the nozzle and for increasing the pressure of the refrigerant by converting velocity energy into pressure energy by mixing the refrigerant ejected from the nozzle with the refrigerant drawn from the evaporator; a gas-liquid separator for storing refrigerant after separating the refrigerant into a gas-phase state and a liquid-phase state, for supplying gas-phase refrigerant to the compressor, and for supplying liquid-phase refrigerant to the evaporator; and a hot-gas passage for guiding the refrigerant discharged from the compressor to the evaporator while bypassing at least the ejector, wherein inflow-preventing means is provided for preventing the refrigerant from flowing into the hot-gas passage during a normal operation, in which the refrigerant is evaporated in the evaporator.
Therefore, the refrigerant transferred from the low pressure part (near the evaporator) into the hot-gas passage 600 is prevented from being retained in the hot-gas passage; thus the required amount of refrigerant is reduced, and the cost of manufacturing the ejector circuit is reduced.
In another aspect, the invention includes a compressor for drawing and compressing refrigerant; a radiator for cooling the refrigerant discharged from the compressor; an evaporator for evaporating the refrigerant; an ejector having a nozzle for expanding refrigerant under a reduced pressure by converting pressure energy of the high-pressurized refrigerant flowing out of the radiator into velocity energy, and a suction device for drawing gas-phase refrigerant evaporated in the evaporator by a flow of refrigerant at a high speed being ejected from the nozzle and for increasing the pressure of the refrigerant by converting velocity energy into pressure energy by mixing the refrigerant ejected from the nozzle with the refrigerant drawn from the evaporator; a gas-liquid separator for storing the refrigerant after separating the refrigerant into a gas-phase state and a liquid-phase state, for supplying gas-phase refrigerant to the compressor, and for supplying liquid-phase refrigerant to the evaporator; a drain pan for storing water dropped from at least the evaporator; a hot-gas passage for guiding refrigerant discharged from the compressor to the evaporator by way of at least the drain pan while bypassing at least the ejector, wherein inflow-preventing means is provided for preventing refrigerant from flowing into the hot-gas passage during a normal operation, in which the refrigerant is evaporated in the evaporator.
Therefore, during the normal operation, the refrigerant transferred from the low pressure part (near the evaporator) into the hot-gas passage is prevented from being retained in the hot-gas passage, so that the required amount of refrigerant is reduced, and the cost of manufacturing the ejector circuit is reduced.
If the hot-gas passage is configured to pass through the drain pan, the hot-gas passage is lengthened, which increases the possibility that the amount of refrigerant retained in may increase. However, as described above, the required amount of refrigerant is decreased, so the invention is especially effective when the hot-gas passage is lengthened. Therefore, water such as melt water or condensed water that has frozen and accumulated in the drain pan can be melted by heat, in a defrosting operation, and the required amount of refrigerant can be reduced.
In another aspect, the inflow preventing means may be a check valve that allows the refrigerant to flow only in one direction.
In another aspect, the inflow preventing means may be an electromagnetic valve that opens and closes the hot-gas passage.
Furthermore, in another aspect, the inflow preventing means may be configured such that the hot-gas passage is connected to the upper side of the refrigerant passage through which the liquid-phase refrigerant flowing out of the gas-liquid separator is passed.
Furthermore, in another aspect, the inflow preventing means may be provided in the hot-gas passage on the side of the evaporator and a defrost control valve for opening and closing the hot-gas passage is provided in the hot-gas passage on the side of the compressor.
Therefore, during a normal operation, both the inlet and outlet sides of the hot-gas passage for the refrigerant can be closed, surely preventing the refrigerant from being retained in the hot-gas passage. Therefore, it becomes possible to surely decrease the required amount of refrigerant to be enclosed.